decennial census, but a few years later the PEP numbers or information obtained from administrative records may be more reliable.

An additional issue to consider is how the unreliability of the GQ sampling frame may affect synthetic small-area estimates. A similar effort, the Local Area Unemployment Statistics (LAUS) program of the Bureau of Labor Statistics, uses state-level estimates from the Current Population Survey (CPS) as input to create model-based state-level estimates. It has found that the direct CPS estimates of unemployment for lower levels of geography are not reliable enough to publish (Pfeffermann and Tiller, 2006).

Recommendation 4-5: The Census Bureau should evaluate methods for producing estimates for counties in which group quarters are known to exist based on the frame but are not included in the sample. The simplest method may be to use the county GQ count from the decennial census. A slightly more complex method would be to use a synthetic estimator, or another straightforward small-area estimator. The evaluation would ideally be completed and changes would be implemented before the 2011 ACS data products are released.


Given that small-area estimates based on the 5-year data are expected to be unreliable in some areas in which GQ residents represent a large proportion of the population, it will be important to flag data products that are affected by the presence of group quarters for a particular geography. This should be considered in addition to publishing the margins of error. One approach would be to flag tables applicable to areas in which there are group quarters in the administrative area but not in the sample.

Recommendation 4-6: In addition to continuing to publish margins of error to accompany the estimates, the Census Bureau should also develop a system for flagging estimates that are adversely affected by the presence of group quarters in the area. This procedure should continue until alternative methodologies are developed to reduce the variance in GQ estimates.

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